After 3 years with no issues with my TC-P42ST30, the display has gone dark and sound has ceased

The display went dark during a short period of use. No sound or picture. Front power LED stays illuminated red.

I unplugged the power cord for about 30 minutes and plugged it back in. When I press the On button on the front panel I can hear a few micro-relays click and the power light turns on red. But still no sound or picture. Also, I can not turn the set off (red power light off) with the remote or the front panel power button (Lock Mode per service manual). I have to unplug the power cord.

When the front red led is on, and I hold down the power button, it will blink 14 times repeatedly.

Any suggestions?

This happened to me as well.

We heard intermittent tones from the Verizon FIOS hardware mounted in the foyer
closet. SHortly thereafter, the pic and sound were lost. The remote (either the Verizon
or Panasonic) will power up the TV but there is no pic or sound. The power
lamp is continuously illuminated. We still have internet access via Verizon's
wireless router as well as Verizon telephone service. All three services enter
the house via the hardware mounted in the foyer closet. The Verizon remote
will cause the channels to change on the converter box as well. The TV is
Panasonic Viera TC-P42S30 and its less than 3.5yrs old.

After messing with this for the last few days, I thought I would seek some help. The TV is the P65ST30. I have an AppleTV connecting to the TV to HDMI 2. I get no sound if I enable Dolby Digital on the Apple TV, but if I disable it, the sound is fine.

I figure it's possible the ST30 can not decode DD signal. So I connect a soundbar with HDMI going through the HDMI 1 ARC port on the TV. I figure even if TV can't decode the signal, ARC will simply cause it to bypass to the sound bar. Nope, no sound there again. Sound does work again when I disable DD, so I know at least the ARC connection is good to the sound bar.

What else am I missing here? I went through the manual a few times for both the TV and the sound bar.

ARC (Audio Return Channel) is to get the sound from OTA (Over the Air) channels from your TV to your receiver when your antenna is connected to your TV. It's just a convenience, so you don't have to run an additional audio wire back to your receiver for OTA.